Meantime the CA EQ Watch continues with special thanks to ESO seismologist Dr Lucy Jones for latest on the gathering swarm

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Earthquake advisory issued for Southern California

Southern California Under Earthquake Advisory

LOS ANGELES - A swarm of earthquakes that rattled the Salton Sea area earlier this week has increased the probability of a major quake hitting Southern California, CBS Los Angeles reports.

The California Office of Emergency Services (OES) issued an earthquake advisory warning residents and officials in Ventura, San Diego, San Bernardino, Riverside, Orange, Los Angeles, Kern and Imperial counties that there was a greater possibility of a major earthquake through Oct. 4.

More than 140 seismic events have been recorded near Bombay Beach along the Salton Sea – a lake that sits on the San Andreas fault northeast of San Diego – beginning Monday and ranging from magnitude 1.4 to 4.3, according to U.S. Geological Survey (USGS) seismologists.

“California is earthquake country. We must always be prepared and not let our guard down,” said OES Director Mark Ghilarducci. “The threat of an earthquake on the San Andreas fault hasn’t gone away, so this is another important opportunity for us to revisit our emergency plans and learn what steps you need to take if a significant earthquake hits.”

The swarm occurred in a region known as the Brawley seismic zone, which is located near a fault network that connects the southernmost end of the San Andreas fault with the Imperial fault.

According to the USGS, preliminary data indicated a roughly one percent chance of a magnitude 7 or greater earthquake being triggered on the Southern San Andreas fault within the next seven days, “with the likelihood decreasing over time.”Scientists say some of the cross-faults are positioned to potentially add stress to the San Andreas fault and the San Jacinto fault system when they rupture.

In a tweet posted on Friday, seismologist Dr. Lucy Jones said the swarm “is over & increased risk mostly gone” – although she followed up with a tweet saying that doesn’t mean “no threat.”

Natural disasters are becoming increasingly commonplace, but more often than not, they happen aboard as opposed to within the borders of the United States. According to a new report from NASA’s Jet Propulsion Lab, that’s going to change before the end of the decade when a massive earthquake strikes California.

In the October 7th edition of the Earth and Space Science journal, scientists from the JPL wrote that after examining the area surrounding the 5.1 magnitude earthquake that hit La Habra, California in 2014, there is a 99.9% chance that another quake of 5.0 magnitude or greater will surface near the Los Angeles area before April 1st, 2018.

“When the La Habra earthquake happened, it was relieving some of that stress, and it actually shook some of the upper sediments in the LA basin and moved those a little bit more,” JPL geophysicist Dr. Andrea Donnellan told CBS Los Angeles.

“There’s enough energy stored to produce about a magnitude 6.1 to 6.3 earthquake.”

There are independent sources that disagree with JPL’s shockingly high percentage, but the consensus is clear: earthquakes happen in bunches, and it’s best to err on the side of caution when lives and infrastructure are at stake.

The scientists aren’t able to make a precise prediction regarding the quake’s location, but they have narrowed it down to within 62 miles of the epicenter of the La Habra quake. Earthquakes are not uncommon in California, but one this large could be frighteningly destructive in a crowded city like Los Angeles, especially if it tilts toward the higher end of the scale."

Natural disasters are becoming increasingly commonplace, but more often than not, they happen aboard as opposed to within the borders of the United States. According to a new report from NASA’s Jet Propulsion Lab, that’s going to change before the end of the decade when a massive earthquake strikes California.

In the October 7th edition of the Earth and Space Science journal, scientists from the JPL wrote that after examining the area surrounding the 5.1 magnitude earthquake that hit La Habra, California in 2014, there is a 99.9% chance that another quake of 5.0 magnitude or greater will surface near the Los Angeles area before April 1st, 2018.

“When the La Habra earthquake happened, it was relieving some of that stress, and it actually shook some of the upper sediments in the LA basin and moved those a little bit more,” JPL geophysicist Dr. Andrea Donnellan told CBS Los Angeles.

“There’s enough energy stored to produce about a magnitude 6.1 to 6.3 earthquake.”

There are independent sources that disagree with JPL’s shockingly high percentage, but the consensus is clear: earthquakes happen in bunches, and it’s best to err on the side of caution when lives and infrastructure are at stake.

The scientists aren’t able to make a precise prediction regarding the quake’s location, but they have narrowed it down to within 62 miles of the epicenter of the La Habra quake. Earthquakes are not uncommon in California, but one this large could be frighteningly destructive in a crowded city like Los Angeles, especially if it tilts toward the higher end of the scale."

Unexpectedly deep seismic activity found along California fault

The Los Angeles area sits atop several fault lines.

With Alert Compliments

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"In Southern California, scientists listening to rumblings deep underground found seismic activity at deeper-than-expected levels, and it may signal new earthquakeextremes, according to a new study.

Deeper or smaller seismic activity can be very difficult to monitor, especially in urban areas, due to the distance between seismicity monitors and the noise caused by traffic and industry. In order to better see these so-called micro signals, a group of researchers temporarily deployed detectors along the Newport-Inglewood fault (NIF), which stretches nearly 50 miles (80 kilometers), from Culver City to Newport Beach, in Southern California.

“It’s very helpful for us to do these kinds of studies where the seismic risk is high because of the dense concentrations of population,” study lead author Asaf Inbal, a geophysics graduate student at the California Institute of Technology, told Live Science. “Most of the damage is inflicted by large earthquakes, but these small earthquakes like the ones we observe at NIF occur much more frequently, and their location can be used to highlight active faults and their depth.” [Image Gallery: This Millennium’s Destructive Earthquakes]

Terrifying earthquakes in modern history

By filtering out the noise, the researchers found that activity along the NIF was unusually deep and frequent compared to similar faults in the region. The researchers said these signals could lead to a better understanding of the depths at which earthquakes can occur, and could further illuminate the structure of the fault.

“Many of these micro earthquakes are deeper than expected. They occur below the crust, in the upper mantle, where rocks are usually thought to be too hot to start quakes (mantle rocks are viscous, they deform like very thick honey, without breaking),” co-author Jean Paul Ampuero, a professor of seismology at Caltech, told Live Science in an email. “They are concentrated in what appears to be the deep continuation of the Newport Inglewood fault down into the upper mantle.”

The Long Beach seismicity sensors can be seen as green dots along the surface, with red representing areas of intense earthquake activity 15-20 miles (25-32 km) deep.Credit: Courtesy of Asaf Inbal

The unexpected depths of these earthquakes raise questions about quake monitoring. Scientists don’t know whether these temblors are widespread and have simply been missed at other faults because of the difficulty in monitoring small, deep quakes, or, if the NIF is unique and somehow the fault has deep seismicity that extends to the upper mantle, the researchers said.

While researchers said they do not yet know the answer, NIF stood out in another way: the frequency of its quakes. Inbal said earthquakes statistically follow a scaling law that predicts the ratio between the number of small and large earthquakes that will occur on a specific fault segment.

“That ratio is generally constant. Along many faults we see the same ratio, though the actual numbers may vary,” Inbal said. “However, on the NIF we find that for the deeper sections of the fault, the number of the small earthquakes is much larger than the number of large earthquakes.”

The researchers suggested that the different ratio along the NIF could be due to changes in temperature, pressure or the mineralogy of the rocks at those depths, but said that further research is needed to determine the root cause.

The NIF’s unique frequency and depth of earthquakes could also mean that the maximum depth of seismic activity may be much deeper than was previously thought, the researchers said.

For example, the 2012 Sumatra earthquake in Indonesia occurred deep beneath the Indian Ocean, penetrating much deeper than expected based on previous measures of seismicity, according to the researchers.

“Since then, we’ve been wondering if something similar could happen on continental faults like in California,” Ampuero said. “Our discovery of deep quakes in Long Beach tells us that the deep roots of a continental fault can still generate quakes.”

Fortunately, this research thus far does not show that these deep fault regions will produce larger earthquakes. The last major earthquake along the NIF was the 6.4-magnitude Long Beach earthquake that struck south of Los Angeles on March 10, 1933.

“Bottom line: We need to do more research about these deep, little quakes,” Ampuero said. “Deploying more of these hyperdense seismic networks is one way forward.”